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KMID : 0364820100460020122
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Korean Journal of Microbiology
2010 Volume.46 No. 2 p.122 ~ p.126
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Phenotypic Suppression of Rad53 Mutation by CYC8
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Park Kyoung-Jun
Choi Do-Hee
Kwon Sung-Hun
Kim Jun-Ho
Bae Sung-Ho
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Abstract
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RAD53 functions as an effector kinase of checkpoint pathways in Saccharomyces cerevisiae, which plays a central role to regulate many downstream cellular processes in response to DNA damage. It also involves in transcriptional activation of various genes including RNR genes which encode the key enzyme required for dNTP synthesis. In this study, we identified CYC8 as a suppressor for the hydroxyurea sensitivity of rad53Δ mutation. Rad53Δ mutant transformed with a multi-copy plasmid containing CYC8 showed increased hydroxyurea resistance. In contrast, TUP1 which forms a complex with CYC8 did not function as a suppressor. In the case of mutations, both cyc8Δ and tup1Δ suppressed hydroxyurea sensitivity of rad53Δ . Since CYC8 can propagate as a prion in yeast, overexpression of CYC8 induced misfolding of the normal CYC8 proteins, resulting in dominant cyc8- phenotype. Therefore, it is suggested that CYC8 can act as a multi-copy suppressor due to its prion property. It was observed that the levels of RNR transcription were increased in the yeast strains containing either multi-copies of CYC8 gene or cyc8Δ mutation, suggesting that the increased level of RNR will elevate the intracellular pools of dNTPs, which, in turn, suppress the phenotype of rad53Δ
mutation.
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KEYWORD
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CYC8, prion, RAD53, ribonucleotide reductase, TUP1
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